1. Field of the Invention
The present invention relates to a fuel injection rail employed in a fuel injection system for an automotive engine.
2. Description of the Related Art
In a fuel supply system for supplying fuel to an automotive engine, a fuel supply pump delivers the fuel to send the fuel through a fuel feed line to a fuel injection rail. The fuel injection rail distributes the fuel to injectors attached to the fuel injection rail. The injectors spray the fuel into an intake manifold connected to an engine.
Referring to FIG. 6 showing a conventional fuel injection rail, the fuel injection rail has a rail body 10 consisting of two pan-shaped members having the shape of a pan, namely, an upper pan-shaped member 10a and a lower pan-shaped member 10b. Injector holding cups 12 are attached to the lower wall of the lower pan-shaped member 10b. A fuel inlet pipe 14 is connected to one end of the rail body 10. The upper pan-shaped member 10a and the lower pan-shaped member 10b are formed by deep draw stamping. The upper pan-shaped member 10a and the lower pan-shaped member 10b are assembled together and are brazed together by braze furnace the joint thereof.
Problems arise in brazing together the upper pan-shaped member 10a and the lower pan-shaped member 10b which are formed by deep draw stamping by brazing. It is very difficult to form the upper pan-shaped member 10a and the lower pan-shaped member 10b accurately in design dimensions by deep draw stamping. Over wrap area of the side walls of the lower pan-shaped member 10b are inserted in a space between the side walls of the upper pan-shaped member 10a as shown in FIG. 7. It is difficult to form the upper pan-shaped member 10a and the lower pan-shaped member 10b by deep draw stamping such that a uniform clearance is formed between the over wrap area of the side wall of the lower pan-shaped member 10b and the corresponding over wrap area of the side wall of the upper pan-shaped member 10a. The quality of brazing the upper pan-shaped member 10a and the lower pan-shaped member 10b is greatly dependent on the accuracy of the clearance. An irregular clearance increases the possibility of defective brazing. Residual stress remains within the upper pan-shaped member 10a and the lower pan-shaped member 10a which are formed by a metal deformation process, namely, deep drawing. When the upper pan-shaped member 10a and the lower pan-shaped member 10b are heated at a high temperature in a braze furnace, the high temperature releases the residual stress and, consequently, a large deformation uncorrectable by a finishing process subsequent to brazing develops in the upper pan-shaped member 10a and/or the lower pan-shaped member 10b. 
It is desirable that the side walls of the rail body of the fuel injection rail are capable of convexly and concavely deforming according to the variation of pressure in the fuel injection rail to lessen the pulsation of the pressure in the fuel injection rail. When the over wrap area of the side walls of the upper pan-shaped member 10a and the lower pan-shaped member 10b are assembled together and copper brazed together by brazing, the thickness of brazed parts of the side walls of the rail body 10 is doubled and the rigidity of the side walls increases. Such an increase in rigidity of the side walls of the rail body 10 is undesirable for the effective absorption of fuel pressure pulsation.